Rational design, efficient syntheses and biological evaluation of N,N'-symmetrically bis-substituted butylimidazole analogs as a new class of potent Angiotensin II receptor blockers.

Abstract A series of symmetrically bis-substituted imidazole analogs bearing at the N-1 and N-3 two biphenyl moieties ortho substituted either with tetrazole or carboxylate functional groups was designed based on docking studies and utilizing for the first time an extra hydrophobic binding cleft of AT1 receptor. The synthesized analogs were evaluated for their in vitro antagonistic activities (pA 2 values) and binding affinities (–logIC 50 values) to the Angiotensin II AT1 receptor. Among them, the potassium (–logIC 50  = 9.04) and the sodium (–logIC 50  = 8.54) salts of 4-butyl- N , N ′-bis{[2′-(2 H -tetrazol-5-yl)biphenyl-4-yl]methyl}imidazolium bromide ( 12a and 12b , respectively) as well as its free acid 11 (–logIC 50  = 9.46) and the 4-butyl-2-hydroxymethyl- N , N ′-bis{[2′-(2 H -tetrazol-5-yl)biphenyl-4-yl]methyl}imidazolium bromide ( 14 ) (–logIC 50  = 8.37, pA 2  = 8.58) showed high binding affinity to the AT1 receptor and high antagonistic activity (potency). The potency was similar or even superior to that of Losartan (–logIC 50  = 8.25, pA 2  = 8.25). On the contrary, 2-butyl- N , N ′-bis{[2′-[2 H -tetrazol-5-yl)]biphenyl-4-yl]methyl}imidazolium bromide ( 27 ) (–logIC 50  = 5.77) and 2-butyl-4-chloro-5-hydroxymethyl- N , N ′-bis{[2′-[2 H -tetrazol-5-yl)]biphenyl-4-yl]methyl}imidazolium bromide ( 30 ) (–logIC 50  = 6.38) displayed very low binding affinity indicating that the orientation of the n -butyl group is of primary importance. Docking studies of the representative highly active 12b clearly showed that this molecule has an extra hydrophobic binding feature compared to prototype drug Losartan and it fits to the extra hydrophobic cavity. These results may contribute to the discovery and development of a new class of biologically active molecules through bis-alkylation of the imidazole ring by a convenient and cost effective synthetic strategy.